There is a general consensus that climate change is an ongoing phenomenon. This will inevitably bring about numerous environmental problems, including alterations to the hydrological cycle, which is already heavily influenced by anthropogenic activity. The available climate scenarios indicate areas where rainfall may increase or diminish, but the final outcome with respect to man and environment will, generally, be detrimental. Groundwater will be vital to alleviate some of the worst drought situations. The paper analyses the main methods for studying the relationships between climate change and groundwater, and presents the main areas in which hydrogeological research should focus in order to mitigate the likely impacts.
Sr and Nd isotopic compositions of a sediment core from the Bay of Bengal are used to constrain the provenance and transport pathways of their terrigenous component during the ∼3 to 34 14C kyr BP. The results clearly demonstrate a distinctly different source for detrital fluxes on the Ninetyeast Ridge from that of distal and western Fan sediments. There is a systematic pattern of climate‐related variability in 87Sr/86Sr and ɛNd(o) values at the studied location. Pulses of low 87Sr/86Sr, higher radiogenic Nd and high silt content occurring at ∼5–7 kyr intervals suggest significant changes in the detrital source. Increased supply of Irrawaddy‐derived sediments appears to be the dominant source for these pulses. Our results support the hypothesis that rapid cold events of North Atlantic (Heinrich events) are characterized by the intensified northeast monsoon.
11High concentrations of fluoride (up to 7.6 mg/L) are a recognized feature of the Wailapally 12 granitic aquifer of Nalgonda District, Andhra Pradesh, India. The basement rocks provide 13 abundant sources of F in the form of amphibole, biotite, fluorite and apatite and whole-rock 14 concentrations of F in the aquifer are in the range 240-990 mg/kg. Calcretes from the shallow 15 weathered horizons also contain comparably high concentrations of F, in the range 635-16 950 mg/kg. The concentrations of water-soluble F in the granitic rocks and the calcretes are 17 usually low (1% of the total or less) but broadly correlate with the concentrations observed in 18 groundwaters in the local vicinity. The water-soluble fraction of calcretes is relatively high in 19 weathered calcretes compared to fresh samples. 20Groundwater major-ion composition shows a well-defined trend with flow downgradient in 21 the Wailapally aquifer, from Na-Ca-HCO 3 -dominated waters in the recharge area at the upper 22 part of the catchment, through to Na-Mg-HCO 3 and ultimately to Na-HCO 3 and Na-HCO 3 -Cl 23 types in the discharge area in the lowest part. The evolution occurs over a reach spanning 24 some 17 km. Groundwater chemistry evolves by silicate weathering reactions, although 25 groundwaters rapidly reach equilibrium with carbonate minerals, favouring precipitation of 26 calcite, and ultimately dolomite in the lower parts of the watershed. This precipitation is also 27 aided by evapotranspiration. Decreasing Ca activity downgradient leads to a dominance of 28 fluorite-undersaturated conditions and consequently to mobilisation of F. Despite the clear 29 downgradient evolution of major-ion chemistry, concentrations of F remain relatively uniform 30 in the fluorite-undersaturated groundwaters, most being in the range 3.0-7.6 mg/L. The rather 31 narrow range is attributed to a mechanism of co-precipitation with and/or adsorption to 32 calcrete in the lower sections of the aquifer. The model may find application in other high-F 33 groundwaters from granitic aquifers of semi-34 arid regions.3
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